It is known to retain the elongated cutter elements, for simplicity hereinafter "cutter strips", by using an additional or separate clamping element or clamping strip which is located in the space between an engagement surface of the cutter strip and the groove and which clamps the cutter strip in position in the groove.
The referenced U.S. Pat. No. 4,360,168, Petersen, describes a cutter of this type in which two strip-like cutter elements are located in lateral recesses of the side walls of a groove, which are clamped in position by a wedge located between the cutter elements. The wedge is pulled by a screw or bolt in the direction of the bottom of the longitudinal groove. The cutter elements have narrow strips which are bounded by parallel lateral flanks, and are not supported radially with respect to the outer circumference. It is necessary to apply substantial clamping forces by the wedge-shaped clamping element, which becomes wider towards the circumference, in order to obtain reliable frictional engagement and holding of the clamping element against the cutter strips. The clamping strip must counteract the centrifugal forces acting on the cutter strips. It is difficult to exchange damaged or worn cutter elements since a substantial number of clamping screws must be loosened. These clamping screws are distributed over the axial length of the tool. The heads of the clamping screws are covered by cover elements and it has been found, from experience, that the wedge-shaped clamping strips, even after loosening of the clamping screws, have a tendency to jam in the grooves and can be released only with difficulty.
A cutter of a different type, see German Pat. No. 22 08 687, Sybertz, uses a cutter structure which is intended for a cutter shaft for a wood working machine, for example a planar or the like. Such cutters are not suited for comminuting of plastics. This cutter uses narrow strip-like laterally supported blades which have parallel flanks and which are fitted in longitudinal grooves of, in cross section, rectangular shape. Looked at from the direction rotation, wedge-shaped clamping elements are located behind the cutter blade strips. A movable intermediate holder is provided, fitted with an interengaging fit on the shaft of the tool, and positioned between the knives and the respective clamping elements, in order to accept and transfer clamping forces for the cutter knives. The clamping elements are supported with respect to the bottom of the longitudinal groove by compression springs. With respect to the cross section thereof, they taper towards the circumference of the cutter blade body, so that, upon operation and application of centrifugal force, they have a tendency to move outwardly to thereby increase the clamping force for the knives. The narrow knives are held radially only by interengaging fits without any specific supports. The intermediate body or holder which is located in the grooves of the tool body is an additional element which has to be carefully made and fitted.